It is proposed to continue the studies of the basis of different response of normal and neoplastic cells to treatment with the adenosine analogue, puromycin aminonucleoside. In particular, to establish if the resistance of neoplastic cells to growth-inhibitory effects of the antimetabolite can be related to the continued synthesis of poly (A)-containing RNA in the presence of aminonucleoside, and to determine the molecular basis for inhibition of poly (A)- RNA synthesis in normal cells treated with aminonucleoside. The principal experimental approach will be to study the patterns of synthesis of individual species of RNA isolated from different sub-cellular locations of cells labeled with radioactive precursors for RNA synthesis. Elucidation of the differences in the expression of normal and neoplastic genome should lead to more effective cancer chemotherapy.